Pioneer GM-A4704 520 Watt Class AB 4-Channel Car Amplifier

Our testing and analysis of the Pioneer GM-A4704

If you’re searching for a 4 channel amplifier to send legitimate power to entry and mid level speakers, consider the Pioneer GM-A4704. This Pioneer 4-Channel amp is an excellent choice to power your front components and rear coaxials on a budget. The Pioneer GMA series amplifiers are Pioneer’s entry level amplifiers, they are Class-AB and provide flexibility with loading down to 2 ohms in stereo mode and 4 ohms in bridged mode. This amplifier is perfect for those just getting started in car audio because it is capable of running in 4 / 3 / and 2 channel modes allowing you to build your first system with just this amp. Pioneer has rated the amp with CTA-2006 compliance, we’ll put that to trial during our testing in a minute.

I consider this amplifier a good deal with a price tag under $160. Pioneer rates this class A/B amplifier 40W RMS x 4 channels @ 4 ohms, 65W RMS x 4 channels @ 2 ohms, and you can also bridge it for 130W x 2 channels @ 4 ohms. Stay tuned in a few minutes for our amplifier power testing to see how accurate these claims are.

What's inside the box?

Inside the box is an instruction manual, hardware, high level speaker level harnesses and 4 channel Pioneer amplifier. It may not look like the most beastly amplifier out there, but the GM-A4704 is moderately powerful but is a definite upgrade to any factory or aftermarket system on a budget. Aesthetically, the GMA series amplifiers are pretty simple. They feature a Satin black chassis with a grey Pioneer logo. One of my favorite features of this amplifier is its Automatic Signal Sensing Turn-On. There is no need to run a remote wire turn on; this amplifier will automatically detect the sound signal and turn on and off the amplifier. Pioneer packed the GM-A4704 with plenty of adjustments for both sets of channels. Channels 1 and 2 feature gain control, variable high-pass filter selectable between 40 Hz - 500 Hz, Fixed 80 Hz LPF and 2 or 4 channel input select switch. Channels 3 and 4 feature gain control, fixed 80 Hz HPF and fixed 80 Hz LPF. All filters are @ 12 dB/octave slopes. There are multiple ways to connect to your source. The GM-A4704 also has two sets of RCA inputs to connect to your signal source using the RCA pre-amp outputs on your aftermarket head unit. Those with factory headunit need not worry, the amplifier features speaker level inputs for all four channels Dimensions of the amplifier include 2-3/8″ H x 8-1/2″ W x 12-7/8″ L For connections the amplifier features four sets of spade connection terminals for speaker outputs. A set of spade terminals for power and ground. We recommend 8-10 gauge power and ground leads, check out our amplifier installation kits online at qualitymobilevideo.com. Pioneer fitted a single 30 amp fuse. It is a Class AB so it will be less efficient than a class D so make sure not to choke this amp with under-sized power cables. Let’s test this amplifier out and see if it hits spec. The first test we ran was 2 channels driven, 4 ohms, 1KHz, 14.3 volts. Our Audio Precision will generate our signal and measure distortion. Our HP8903B Audio Analyzer Picked up 58 W RMS, 1% distortion and 15.1 volts of output. Our AMM-1 read 45 Watts and we drew 13 amps of current. Going down to 40 Hz. Our HP picked up 55W RMS, 1% distortion and 14 volts of output. The AMM-1 read 48 Watts and we drew 13 amps of current. Next we went to 2 channels driven, 2 ohm, 40Hz, 14.3 volts. Our HP picked up 79W RMS, 1% distortion and 12 volts of output. Our AMM-1 read 70 Watts and we drew nearly 22 amps of current. Going up to 1 KHz. Our HP picked up 85W RMS, 1% distortion and 13 volts of output. Our AMM-1 read 69 Watts and we drew nearly 22 amps of current. Our final test was on frequency response, we used our audio precision to run up each frequency.

Car amplifier installation

We show you the complete process of installing a Pioneer Double DIN car stereo in a Chevy truck. The in-depth video shows the installation of the interface, and steering wheel control.

Amplifier Installation basics

Let's start with the basics of adding or installing a car amplifier. First you will need to plan your installation and power wiring, this usually is the most difficult part of the installation for most.

How to choose the proper wire size explained

What size power wire do I need for my amplifier? Well, that depends on the length of the wire and the power consumption of the amplifier. We walk you through how to choose the right gauge wire and wire material depending on your amplifier installation requirements.

How to wire speakers and subwoofers to your new amplifier

In our third video we demonstrate the various ways you can wire speakers and amplifiers to all types of amplifiers. There different ways to do this depending on the type of amplifier you choose to purchase.

What is gain? How do I set it properly?

In our fourth video we demonstrate how to set the gains on your amplifier to prevent damage to your speakers, subwoofers and even possibly your new amplifier. Using a portable oscilloscope we show you how to set your gains.